Got a new SIM card, eSIM or swapped your SIM? Here’s what to know about SMS, UPI, OTPs and bank transactions

SIM Swap limitations

• TRAI mandates 24-hour SMS block after SIM swap to prevent fraud
• Banking OTPs and UPI app logins may not work during this period
• SMS services resume automatically after 24 hours

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You must have noticed that whenever you buy a new SIM card or get it swapped or move to eSIM, there are are certain limitations that tags along with the process. And, no that's not the network or activation time I am talking about. The biggest pain point is the restriction of certain services  after a SIM replacement or swap. To be specific, that restriction is set for 24 hours and that's a part of government's norm to prevent SIM Swap scams and frauds.

The Telecom Regulatory Authority of India (TRAI) has mandated security rules that restrict certain services immediately after a SIM replacement or swap. These measures are designed to prevent financial fraud and unauthorized access to banking accounts. As a result, SMS services related to banking and digital payments may stop working for a limited period.

24-hour SMS restriction after SIM replacement

After a SIM swap, SIM replacement, or eSIM transfer, telecom operators must block incoming and outgoing SMS services for 24 hours. This rule is mandated by TRAI to reduce the risk of SIM swap fraud, where criminals try to gain control of a victim’s phone number.

During this period, users will not receive SMS messages from banks or payment platforms. This includes One-Time Passwords (OTPs) required for authentication. Because many banking and payment systems rely on SMS verification, several services temporarily stop working during this time.

Once the 24-hour restriction ends, SMS functionality is automatically restored and normal services resume.

UPI apps and device verification

Unified Payments Interface (UPI) apps depend on SMS verification to confirm the identity of the device linked to a mobile number. Because of this requirement, users may face issues accessing payment apps immediately after a SIM change.

During the SMS suspension period, users cannot log into or activate apps such as Google Pay, PhonePe, or Paytm. These applications send a verification SMS to confirm that the mobile number is active on the device.

After the 24-hour block is lifted, users must reopen the UPI application and complete the verification process again. The app will send an SMS from the device to confirm ownership of the number. Once the process is completed, the device is linked again and UPI services resume.

Bank transactions and OTP delivery

Banking services that depend on SMS-based authentication may also stop working temporarily after a SIM replacement. This includes online payments, fund transfers, and certain internet banking logins that require OTP verification.

Users may not receive OTP messages for card payments or banking transactions during the SMS restriction period. In addition, banks may not be able to send SMS alerts for account activity such as deposits or withdrawals.

If a bank provides alternative authentication methods such as email OTPs or hardware security tokens, those options may continue to work during the SMS suspension.

Steps required when switching mobile numbers

If a user changes their mobile number entirely, additional steps are required to restore banking and UPI services.

The account holder must first request their bank to update the registered mobile number linked to their account. This usually requires visiting a bank branch or submitting identity documents through official channels.

After the bank updates the number, users must register their UPI ID again with the new mobile number. The earlier UPI ID linked to the previous number stops functioning once the number change is processed.

Following these steps ensures banking alerts, OTP verification, and digital payments work correctly with the updated number.

Now, let's understand how exactly this prevents frauds and scams:

Why did my bank OTP stop coming after I replaced my SIM?”

That usually happens because of a security rule. After a SIM replacement or an eSIM transfer, telecom operators temporarily block SMS services for 24 hours.

“But why block SMS?”

It’s mainly to prevent SIM swap fraud. In these cases, criminals try to get a duplicate SIM linked to someone else’s phone number. Once they control that number, they can receive OTPs and banking alerts.

“So the SMS block stops that?”

Exactly. Because SMS is suspended for a short period, OTPs for bank transactions, UPI verification, and account logins cannot be received immediately after the SIM change.

“And how does that help users?”

The delay makes it harder for fraudsters to access financial accounts or complete transactions. It also gives the real user time to notice if something unusual has happened with their number and report it to their telecom operator or bank.